Refactor PostgreSQL provider: multi-schema & async prep

- Refactor migrations and provider to use multiple PostgreSQL schemas, each matching a legacy SQLite database (activitylog, authentication, displaypreferences, library, users).
- All tables, foreign keys, and indexes are now schema-qualified; Down migration drops tables by schema.
- Provider ensures schemas exist before migrations; entities are mapped to correct schemas in OnModelCreating.
- Add support for max-pool-size, min-pool-size, and multiplexing connection options; update logging accordingly.
- VACUUM ANALYZE now runs per schema during scheduled optimization.
- TruncateAllTablesAsync now truncates tables with schema qualification.
- README updated with schema structure, new options, and multiplexing warnings.
- CacheDecorator now calls async repository methods using .GetAwaiter().GetResult(), with documentation.
- Lays groundwork for full async/await and multiplexing support in the database layer.

MediaBrowser.Controller/Persistence/IItemRepository.cs

@@ -61,6 +61,14 @@ public interface IItemRepository
     /// <returns>QueryResult&lt;BaseItem&gt;.</returns>
     QueryResult<BaseItem> GetItems(InternalItemsQuery filter);
 
+    /// <summary>
+    /// Gets the items asynchronously.
+    /// </summary>
+    /// <param name="filter">The query.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>QueryResult&lt;BaseItem&gt;.</returns>
+    Task<QueryResult<BaseItem>> GetItemsAsync(InternalItemsQuery filter, CancellationToken cancellationToken = default);
+
     /// <summary>
     /// Gets the item ids list.
     /// </summary>
@@ -68,6 +76,14 @@ public interface IItemRepository
     /// <returns>List&lt;Guid&gt;.</returns>
     IReadOnlyList<Guid> GetItemIdsList(InternalItemsQuery filter);
 
+    /// <summary>
+    /// Gets the item ids list asynchronously.
+    /// </summary>
+    /// <param name="filter">The query.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>List&lt;Guid&gt;.</returns>
+    Task<IReadOnlyList<Guid>> GetItemIdsListAsync(InternalItemsQuery filter, CancellationToken cancellationToken = default);
+
     /// <summary>
     /// Gets the item list.
     /// </summary>
@@ -75,6 +91,14 @@ public interface IItemRepository
     /// <returns>List&lt;BaseItem&gt;.</returns>
     IReadOnlyList<BaseItem> GetItemList(InternalItemsQuery filter);
 
+    /// <summary>
+    /// Gets the item list asynchronously.
+    /// </summary>
+    /// <param name="filter">The query.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>List&lt;BaseItem&gt;.</returns>
+    Task<IReadOnlyList<BaseItem>> GetItemListAsync(InternalItemsQuery filter, CancellationToken cancellationToken = default);
+
     /// <summary>
     /// Gets the item list. Used mainly by the Latest api endpoint.
     /// </summary>
@@ -98,8 +122,24 @@ public interface IItemRepository
 
     int GetCount(InternalItemsQuery filter);
 
+    /// <summary>
+    /// Gets the count of items asynchronously.
+    /// </summary>
+    /// <param name="filter">The query.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The count.</returns>
+    Task<int> GetCountAsync(InternalItemsQuery filter, CancellationToken cancellationToken = default);
+
     ItemCounts GetItemCounts(InternalItemsQuery filter);
 
+    /// <summary>
+    /// Gets the item counts asynchronously.
+    /// </summary>
+    /// <param name="filter">The query.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The item counts.</returns>
+    Task<ItemCounts> GetItemCountsAsync(InternalItemsQuery filter, CancellationToken cancellationToken = default);
+
     QueryResult<(BaseItem Item, ItemCounts ItemCounts)> GetGenres(InternalItemsQuery filter);
 
     QueryResult<(BaseItem Item, ItemCounts ItemCounts)> GetMusicGenres(InternalItemsQuery filter);